Catherine G. Marzin, a researcher with the federal government's National Marine Sanctuary Program, didn't know what awaited her that morning in the French naval archives outside Paris.

She was on the trail of one Brutus De Villeroi, a 19th-century French inventor who in 1861 designed the U.S. Navy's first submarine. The archives didn't have a biographical file on him. But the agency did have a box of his papers.

When Marzin, 34, opened the box in May and extracted file 3084, she was stunned. Inside were hand-drawn antique sketches of a vessel shaped like a fountain pen. It had a series of tiny portholes, a diver's chamber and strange, folding oars sticking out of its sides. "PLANS du Bateau Sous-Marine," the drawings said: Blueprints of the Submarine Ship.

"Bingo!" Marzin said to herself.

Today, the Navy and the National Oceanic and Atmospheric Administration, which oversees the sanctuary program, will formally announce the government's discovery of the plans for the historic USS Alligator and renew calls for a search for the forgotten vessel, which sank in a storm off Cape Hatteras, N.C., in 1863.

"It's like finding a photograph of a person you're doing historical research on, but you have no idea what they look like," said Jim Christley, a veteran of the Navy's submarine service and a submarine historian who has been researching the Alligator for years.

"It adds a lot of information that you didn't have before, stuff that you were only guessing about," Christley, 58, of Lisbon, Conn., said in a telephone interview last week.

"It answers questions for people who want to know hard facts: What does it look like? You can say: Here's what we think it looks like. This is what the designer intended."

Marzin's "finding those blueprints was an absolute jewel in the crown," he said. "And the luck that she had in being able to do that is really incredible."

Little is known about the weird green boat called the Alligator, despite its status as the progenitor of the Navy's submarine service, said Daniel Basta, director of the Silver Spring-based Office of Marine Sanctuaries.

It never engaged in combat, although it was the first Navy sub to be deployed to a combat zone. And it was at first powered, unglamorously, by oars.

Its story has been eclipsed by that of the better known Confederate Civil War submarine, H.L. Hunley, which sank a Union warship in 1864 but was lost in the process. The Hunley was raised from the ocean off Charleston, S.C., in 2000 with the remains of its crew still on board.

Nor is much known about the Alligator's inventor, De Villeroi, a printer's son who later claimed to be a French knight and told the U.S. Census that his occupation was "natural genius." He spent much of his life tinkering with submarine designs, and historians believe he might have influenced 19th-century French science fiction author Jules Verne, who was a math student of De Villeroi's.

The 47-foot-long Alligator was constructed of rolled iron in a shipyard in Philadelphia, where De Villeroi had immigrated, and was launched May 1, 1862, according to Christley and Michiko Martin of the Marine Sanctuary Program. The Navy had turned to submarine technology to help counter Confederate technological advances in such iron-clad warships as the CSS Virginia, known in the North as the Merrimack.

De Villeroi had been experimenting with submersible boats in the Delaware River, and an early sub was confiscated in 1861 by Philadelphia police, who suspected "treasonable purposes," according to a newspaper account at the time.

Unlike the Hunley, which had a torpedo on the end of a long spar, the Alligator used a hard-hat diver to launch attacks.

The Alligator had a lockout chamber that a diver, tethered to an air line, could use to leave the boat, Christley said. Carrying an explosive charge connected to the boat with electrical wires, the diver swam to the enemy vessel, attached the charge to the vessel's hull and returned to the sub. The charge would then be detonated by electricity.

It was closer to modern Navy special operations than what later evolved into submarine warfare. The Alligator was not a "blue water" boat, Christley said, and was designed to operate in rivers and harbors.

In some ways, the sub was worthy of Verne, whose fictional Victorian boat, the Nautilus, figured in his 1870 novel, "20,000 Leagues Under the Sea."

The Alligator had a crew of 20, along with a rudimentary air purification system to scrub out carbon dioxide. It probably had a crude air compressor to serve the diver, Christley said.

Its initial design was equipped with specialized underwater oars, eight to 10 on each side, which poked through the hull. They were supposed to give the boat maneuverability.

Oars made for slow speed, though, and they later were replaced with a single screw propeller in the stern.

In spring 1862, the Alligator was deployed to the Hampton Roads area of Virginia to help clear enemy river obstructions and blow up an important railroad bridge. But the rivers were too shallow, and Navy officials feared the Alligator might be captured by the rebels.

It was moved to the Washington Navy Yard for alterations and more testing. President Abraham Lincoln, who was fascinated with technology, is believed to have watched some of the testing, Christley said.

In the spring of 1863, the Alligator got a new assignment: It was to deploy to the coast of South Carolina for operations against Charleston, Maryland author Mark K. Ragan wrote in his 1999 book, "Submarine Warfare in the Civil War."

But on the evening of April 2, 1863, the boat was lost in a storm off Cape Hatteras as it was being towed south by an escort ship. After that, Ragan said last week, "It was basically forgotten by history."

While periodic scholarship on the Alligator has been conducted over the past century, new attention has come from Rear Adm. Jay Cohen, head of the Office of Naval Research. Cohen told Basta about the sub when both were involved in the successful South Pacific search last year for President John F. Kennedy's sunken torpedo boat, PT-109.

The Navy and NOAA began new research, which led to Marzin's trip to the French archives.

Basta, 56, said he believes the blueprints could help a search for the lost submarine, which might lie in 10,000 feet of water just off the continental shelf.

The plans could provide clues to how fast the boat sank, Basta said, which could help point to where it sank.

It would be "an extraordinarily difficult thing to find," Basta said.

"It is a huge challenge to our science. But I believe if we can find the 109, we can find the Alligator."

Tim, you utterly amaze me. How do you come up with this stuff? Now I really am having a hard time restraining myself from jumping right into the project. The drawings are pretty close to what Ragan published in his book, though far more detailed. Alas, yet another antique boat without a circular cross section (sigh ) [Must - control - urge - to - start - new - sub! Must - control........]

George "Crazy Ivan" Protchenko

“There are the assassins, the dealers in death; I am the Avenger!”-Nemo"I'm disinclined to acquiesce to your request; means No!"-Capt.Barbossa